Carbon Composite Materials and Methods of Manufacturing Same

ABSTRACT

A method for manufacturing a carbon composite is provided. The method includes providing a carbon-containing resin material to which an appropriate concentration of catalyst particles may be added. Thereafter, the catalyzed resin may be subject to a high temperature range, at which point carbon in the resin to begins to couple to the catalyst particles. Continual exposure to high temperature leads to additional attachment of carbon to existing carbon on the particles. Subsequently growth, within the resin material, of an array of carbon nanotubes occurs, as well as the formation of the composite material.

RELATED US APPLICATION(S)

The present application claims priority to U.S. Provisional PatentApplication Ser. Nos. 60/677,116, filed May 3, 2005 and 60/760,748,filed Jan. 20, 2006, both of which are hereby incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to carbon composites and methods ofmanufacturing same, and more particularly, to a carbon composite havinga relatively high loading of carbon nanotubes.

BACKGROUND ART

Carbon nanotubes are known to have extraordinary tensile strength,including high strain to failure and relatively high tensile modulus.Carbon nanotubes may also be highly resistant to fatigue, radiationdamage, and heat. To this end, the addition of carbon nanotubes tocomposites can increase tensile strength and stiffness. Examples ofcomposites that have incorporated nanotubes include epoxy-nanotube,Krayton-nanotube, PEEK (polyaryletherketone)-nanotube, phenylformaldehyde-nanotube, RESOL-nanotube, furfuryl alcohol-nanotube,pitch-nanotube, latex-nanotube, polyethylene-nanotube,polyamide-nanotube, or carbon-carbon (nanotube) composites.

Unfortunately adding even a small amount of carbon nanotubes to, forinstance, a resin matrix to subsequently generate the desired compositecan increase the viscosity of the matrix significantly. As a result, amaximum of only between 1% to 5% by weight of carbon nanotubes may beadded to a resin using current mixing technology.

Accordingly, it would be advantageous to provide a method formanufacturing a composite having a relatively high amount of carbonnanotubes, so that a composite with low density and high modulus andstrength may be created. In addition, it would be advantageous toprovide a carbon nanotube composite with such characteristics.

SUMMARY OF THE INVENTION

The present invention, in one embodiment, is directed to a method formanufacturing a composite, whereby at least one sheet of non-wovencarbon nanotubes or nanofibers may be infiltrated with an appropriateresin. In accordance with an embodiment, the method includes initiallylayering a plurality of non-woven sheets of carbon nanotubes. Next, aresin material may be applied to the non-woven sheets to infiltratevoids between the carbon nanotubes with a resin material. In anembodiment, each non-woven sheet may be coated with a resin material.Alternatively, a sheet of polymeric resin may be situated betweenadjacent non-woven sheets and melted into the voids. To the extentnecessary, prior to infiltrating the voids with a resin material, asurface treatment process can be applied to the carbon nanotubes tofacilitate bonding of the resin material to the nanotubes. Theinfiltrated sheets may thereafter be bonded with one another to providea formed mass or structure. The infiltrated sheets may then be exposedto a temperature range of from about 1000° C. to about 2000° C. totransform the infiltrated sheets into the composite material.

In another embodiment, the present invention provides another method inwhich a suitable catalyst may be added to a high-carbon-containing resinto generate an in situ composite having a glassy carbon matrixreinforced by a “grown-in” array of carbon nanotubes. The methodincludes initially providing a carbon-containing resin material. Next,an appropriate concentration of catalyst particles may be added to thecarbon-containing resin material. In one embodiment, the concentrationof the catalyst particles can be about 0.005 percent to about 5 percentby weight of catalyst particles to carbon in the resin material.Thereafter, the catalyzed resin may be placed in an inert atmosphere andsubject to a temperature range of from about 1000° C. to about 2000° C.,at which point carbon in the resin to begins to couple to the catalystparticles. Continual attachment of carbon to the particles andsubsequently to existing carbon on the particles can lead to the growth,within the resin material, of an array of carbon nanotubes and theformation of the composite material. In an embodiment, a sulfurcontaining compound may be added to the catalyzed resin to augmentsubsequent activities of the catalyst particles when the catalyzed resinis subject to high temperature.

The present invention further provides a composite material having amass having a thickness ranging from about 0.01 mm to more than about 3mm. The composite also includes a plurality of non-woven nanotubesdispersed throughout the mass, such that a plurality of voids existsbetween the nanotubes. The composite further includes a resin materialsituated within the voids between the non-woven nanotubes to provide themass with structural integrity. In an embodiment, the amount ofnanotubes that exist in the composite can be more than about 5% byvolume of the mass. Moreover, the resin material may differ in differentareas of the mass so as to provide the mass with different properties inthose areas.

In another embodiment, the present invention provides a compositematerial having a glassy carbon matrix. The composite material alsoincludes a plurality of catalyst particles dispersed throughout thematrix. The composite material further includes an array of nanotubes,each extending from a catalyst particle, so as to provide the glassycarbon matrix with added structural integrity. The catalyst particles,in an embodiment, can act as an x-ray contrasting agent, and to theextent the catalyst particles have magnetic properties, can act toprovide magnetic properties to the composite. In addition, the amount ofnanotubes that exist in the composite can be more than about 5% byweight of the mass. Moreover, the resin material may differ in differentareas of the mass so as to provide the mass with different properties inthose areas.

The present invention also provides a stent for placement within avessel. The stent, in an embodiment, includes a tubular expandablematrix having a plurality of intersecting filaments. The stent alsoincludes a plurality of nanotubes situated within a core of eachfilament. In one embodiment, a glassy carbon material may be situatedabout the nanotubes. The stent further includes a pathway extending fromone end of the tubular matrix to an opposite end to permit fluid withinthe vessel to flow therethrough, and having a surface defined by theglassy carbon material. In an embodiment, a patterned surface may beprovided about the tubular matrix to permit the matrix to engage againsta surface of the vessel, so as to minimize its movement within thevessel.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates sheets of non-woven carbon nanotubes for use in themanufacture of a carbon-carbon composite in accordance with oneembodiment of the present invention.

FIG. 2 illustrates sheets of non-woven carbon nanotubes for use in themanufacture of a carbon-carbon composite in accordance with anotherembodiment of the present invention.

FIG. 3 illustrates a glassy carbon matrix composite manufactured inaccordance with another embodiment of the present invention.

FIGS. 4A-B illustrate a stent made from a composite material of thepresent invention.

FIGS. 5A-B illustrate various matrix or filament designs for use withthe stent of the stent illustrated in FIGS. 4A-B.

FIG. 6 is a cross-sectional view of a filament of the stent illustratedin FIG. 4.

FIG. 7A-B illustrate one patterned design for an exterior surface of thestent shown in FIG. 4 to permit anchoring of the stent within a vessel.

FIG. 8 illustrates other patterned designs for use in connection withthe stent in FIG. 4.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Carbon nanotubes for use in connection with the present invention may befabricated using a variety of approaches. Presently, there existmultiple processes and variations thereof for growing carbon nanotubes.These include: (1) Chemical Vapor Deposition (CVD), a common processthat can occur at near ambient or at high pressures, (2) Arc Discharge,a high temperature process that can give rise to tubes having a highdegree of perfection, and (3) Laser ablation.

At present, CVD appears to be one of the more attractive approaches froma commercial standpoint for fabricating carbon nanotubes. However, sincegrowth temperatures for CVD can be comparatively low ranging, forinstance, from about 600° C. to about 1300° C., carbon nanotubes, bothsingle wall (SWNT) or multiwall (MWNT), may be grown, in an embodiment,from nanostructural catalyst particles supplied by reagentcarbon-containing gases (i.e., gaseous carbon source).

Examples of catalyst particles that may be used in connection with CVDinclude ferromagnetic transition metals, such as iron, cobalt, nickel,oxides, nitrates or chlorides of these metals. In certain instances,these catalyst particles may be combined with molybdenum or ceramiccarriers or with each other. In the case of oxides, the oxides may bereduced to metallic form, as a result of the excess of hydrogen presentin these reactions.

Suitable carbon-containing gases for the CVD process, in one embodiment,can include acetylene, methane, ethylene, ethanol vapor, methanol vaporand the like.

Although there exist a variety of CVD processes, an example of a CVDprocess that can be used in connection with the present invention isdisclosed in U.S. Patent Application Publication US 2005/0170089, whichapplication is hereby incorporated herein by reference.

The carbon nanotubes generated for use in connection with the presentinvention may be provided with certain characteristics. In accordancewith one embodiment, diameters of the carbon nanotubes generated may berelated to the size of the catalyst particles. In particular, thediameters for single wall nanotubes may typically range from about 0.5nanometers (nm) to about 2 nm or more for single wall nanotubes, andfrom about 2 nm up to about 50 nm or more for multi-wall nanotubes. Inaddition, it should be noted that the nature of these carbon nanotubes,for instance, their metallic or semiconductor character, may correspondto their diameter, their chirality and/or their defects, if any.Accordingly, in order to control the nature or characteristic of thesenanotubes, it may be necessary to control their dimensions withsufficient accuracy.

Moreover, the strength of the SWNT and MWNT generated for use inconnection with the present invention may be about 30 GPa maximum.Strength, as should be noted, can be sensitive to defects. Nevertheless,the elastic modulus of the SWNT and MWNT fabricated for use with thepresent invention is typically not sensitive to defects and can varyfrom about 1 to about 1.5 TPa. Moreover, the strain to failure, whichgenerally can be a structure sensitive parameter, may range from a fewpercent to a maximum of about 10% in the present invention.

These parameters and characteristics, when taken together, suggest thatthe carbon nanotubes produced by methods of the present invention can bea sufficiently strong material for use in the subsequently production ofa carbon composite.

Carbon-Carbon Composite

The present invention provides, in one embodiment, a process formanufacturing a carbon-carbon composite from at least one sheet ofnon-woven carbon nanotubes or nanofibers (i.e., carbon nanotube paper).

The sheets of non-woven fibers, in an embodiment, may be made byinitially harvesting carbon nanotubes made in accordance with a CVDprocess as disclosed in U.S. Patent Application Publication US2005/0170089, which application is hereby incorporated herein byreference.

Looking now at FIG. 1, the harvested carbon nanotubes 11 may thereafterbe layered in a non-woven, overlapping manner in the presence of abinder material to form a sheet 10, similar to the process for makingpaper. Alternatively, the nanotubes 11 may be wound into fibers and thefibers layered in a non-woven, overlapping manner in the presence of abinder material to form sheet 10. Examples of a suitable binder materialincludes any thermoplastic material including, for example, polyolefinssuch as polyethylene, polypropylene, polybutene-1, andpoly-4-methyl-pentene-1; polyvinyls such as polyvinyl chloride,polyvinyl fluoride, and polyvinylidene chloride; polyvinyl esters suchas polyvinyl acetate, polyvinyl propionate, and polyvinyl pyrrolidone;polyvinyl ethers; polyvinyl sulfates; polyvinyl phosphates; polyvinylamines; polyoxidiazoles; polytriazols; polycarbodiimides; copolymers andblock interpolymers such as ethylene-vinyl acetate copolymers;polysulfones; polycarbonates; polyethers such as polyethylene oxide,polymethylene oxide, and polypropylene oxide; polyarylene oxides;polyesters, including polyarylates such as polyethylene terphthalate,polyimides, and variations on these and other polymers havingsubstituted groups such as hydroxyl, halogen, lower alkyl groups, loweralkoxy groups, monocyclic aryl groups, and the like, and otherthermoplastic meltable solid materials.

Alternatively, the sheets of non-woven carbon nanotubes may be obtainedfrom any commercially available source.

Next, a plurality of non-woven sheets 10 may be next be layered on oneanother and, in one embodiment, be provided with at least one coating ofa resin material, such as furfuryl alcohol (C₅H₆O₂). The coating ofresin material can infiltrate voids 12 between the overlapping carbonnanotubes 11, and subsequently provide structural integrity to theresulting composite material. The amount of furfuryl alcohol used may bedetermined in accordance with the amount of carbon nanotubes 11 in thenon-woven sheet 10. In particular, the ratio of carbon from the furfurylalcohol to the carbon in the nanotubes 11 can range, in an embodiment,from about 1:1 to about 10:1. In an embodiment where a substantiallynon-porous composite may be generated, a ratio of carbon from thefurfuryl alcohol to the carbon in the nanotube 11 may be about 3:1.

It should be noted that coating of the non-woven sheets 10 can beperformed on each individual sheet 10 prior to the sheets 10 beinglayered on one another. Moreover, if desired, prior to infiltrating thevoids with a resin material, a surface treatment process can be appliedto the carbon nanotubes to facilitate wetting (i.e., bonding) of theresin material to the nanotubes. Such surface treatment can beimplemented by methods well known in the art.

The coating of furfuryl alcohol on the sheets 10 of non-woven carbonnanotubes 11 may then be allowed to evaporate and polymerize with thenanotubes 11 at a temperature ranging from about 50° C. to about 150° C.To the extent that the resin material may be available in a polymerizedformed, exposure to heat for polymerization may not be necessary.

Thereafter, the coated sheets 10 may be hot pressed to bond the sheetsof non-woven carbon nanotubes with one another into a formed mass orstructure 13. The pressing, in one embodiment, may be done at atemperature range of from about 125° C. to about 350° C., and at apressure of at least about 3000 psi for approximately 10 minutes oruntil the sheets 10 are bonded to one another. It should be appreciatedthat the temperature, pressure and length of time can be dependent ofthe type of resin selected.

In an alternative embodiment, with reference now to FIG. 2, a thin sheet20 of a polymeric resin, such as RESOL resin, polyamide, epoxy, Krayton,polyethylene, or PEEK (polyaryletherketone) resin, other commerciallyavailable resins, or a combination thereof, may be positioned betweenadjacent sheets 10 of non-woven carbon nanotubes 11.

This sandwich structure 21 of non-woven sheets 10 and resin 20 may thenbe hot pressed to bond the sheets 10 of non-woven carbon nanotubes 11with one another into a form. The pressing, in one embodiment, may bedone at a temperature range of from about 125° C. to about 350° C., andat a pressure of at least about 3000 psi for approximately 10 minutes oruntil bonding of the sheets occurs. By pressing in such a manner, thesheets 20 of polymeric resin may soften and flow to infiltrate voids 12between overlapping carbon nanotubes 11 within each non-woven sheet 10,and permit the non-woven sheets 10 to bond with one another to provide aformed mass or structure 13. Again, the temperature, pressure and lengthof time can be dependent of the type of resin selected.

It should be appreciated that, similar to the coating approach, ifdesired, prior to infiltrating the voids with a resin material, asurface treatment process can be applied to the carbon nanotubes tofacilitate bonding of the resin material to the nanotubes. Such surfacetreatment, again, can be implemented by methods well known in the art.

Once bonded, the sheets 10 of non-woven carbon nanotubes 11 in formedmass 13 may be subject to pyrolysis for curing. In particular, theformed structure 13 may be subject to slowly increasing temperature, forinstance, less than 1 degree C. per minute. In an embodiment, the curingtemperature may be raised to at least between about 1000° C. and about2000° C., and more preferably about 1700° C. to form a carbon-carboncomposite. This slow heating rate, in one embodiment, allows water, aprimary fluid by-product of the reaction, to diffuse out of the formedstructure 13 and permits the structure 13 to be cured into thecarbon-carbon composite.

To the extent desired, this cured or paralyzed carbon-carbon compositemay be hot pressed over or into a mold having a shape of a final productor structure, and may be further pyrolyzed for final curing.Specifically, the composite may be subject to a final ramp temperatureup to about 3000° C. to anneal (i.e., remove any defects) the compositein the shape of the desired product or structure.

Although reference is made to the use of multiple sheets 10 of non-wovencarbon nanotubes 11, it should be appreciated that the only onenon-woven sheet 10 may be used in the manufacturing of a carbon-carboncomposite. The number of sheets 10 employed, in an embodiment, may bedependent on the desired percentage weight of carbon nanotubes per unitarea of the composite to be manufactured. In other words, to obtain arelatively high percentage weight of carbon nanotubes per unit area,additional sheets 10 of non-woven carbon nanotubes 11 may be used.

Moreover, the thickness of each non-woven sheet 10, in an embodiment,can range from about 0.01 mm up to more than about 1 cm. It should beappreciated that curing may need to take into account the time forreaction products to diffuse out of the structure 13. Since the primaryreaction product during this process is a fluid, such as water, theamount of time necessary for curing can be significant for thicknessesof more than about 3 mm.

One method of increasing thickness of each non-woven sheet 10 beyondabout 3 mm may be to coat each layer (i.e., sheet) with a diluted resinon a heated substrate, so that curing of the resin can occur before thenext layer 10 may be applied. Another method of making thicker sheetsand thus composites may be to provide channels within the non-wovensheets 10 to allow reaction products (e.g., water) to escape moreeasily.

It should be noted that in the embodiment where thin sheets 20 ofpolymeric resin may be used, resin sheets of different polymers may bepositioned between different adjacent non-woven sheets 10 to create astructure or device, such as a protective helmet, with differentproperties on the outer surface than in the interior. For example apigmented polymer resin layer may be placed on the outer surface of thecomposite to eliminate painting.

Alternatively, a polymer resin layer containing a roughening element,such as walnut shell fragments presently used in military helmets, canbe incorporated in one molding step. Other types of gradients inproperties may also be advantageous to help distribute impact energyfrom a projectile over a larger volume element. This may be done bylayering the non-woven carbon nanotube sheets 10 close together towardsthe outer layers and spreading them out towards the interior layers,and/or by changing the type of binder used as a function of thethickness.

Moreover, structures or devices made from the composite manufactured inaccordance with this process of the present invention can maintain theirproperties at elevated temperatures. For example, with PEEK resin, thecomposite can be expected to maintain its strengths and properties attemperatures of about 160° C. and usable at temperatures of up to about260° C.

Glassy Carbon Matrix Composite

In accordance with another embodiment of the present invention, there isprovided a process for generating a composite material having a glassycarbon matrix reinforced by a “grown-in” array of carbon nanotubes. Inother words, the process provides an approach wherein an array ofnanotubes may be permitted to form and grow by solid state transportwithin a carbon containing resin material, which resin material maysubsequently be transformed into a glassy carbon matrix composite.

In particular, the process includes initially adding a suitable catalystto a carbon-containing resin. Examples of a suitable catalyst include,ferrocene, iron nano-particles, iron pentacarbonyl, nano-particles ofmagnetic transition metals, such as, cobalt, cobalt hexacarbonyl,nickel, nickel hexacarbonyl, molybdenum or their alloys, or oxides,nitrates or chlorides of these metals or any combination of the oxidesor other reducible salts (e.g., iron ammonium sulfate or iron chloride)or organometallic compounds of these metals. Examples of a suitablecarbon-containing resins for use in the present process include ahigh-carbon-containing resin, such as RESOL resin (i.e., catalyzedalkyl-phenyl formaldehyde), which can be obtained from Georgia Pacific,furfuryl alcohol, or pitch.

The catalyst particles, in an embodiment, may be added at an appropriateconcentration to the carbon-containing resin, so as to provide theresulting composite material with optimal properties. To that end, theconcentration of the catalyst particles used in connection with thepresent invention may be a function of concentration of carbon in theresin. In an example where ferrocene (Fe(C₅H₅)₂) is added tohigh-carbon-containing RESOL phenyl formaldehyde, the concentration offerrocene may range from about 0.005 percent to about 5 percent byweight. More particularly, the ratio of ferrocene may be about 2 percentby weight (iron to carbon). Alternatively, the catalyst particles may besubstantially uniformly dispersed throughout the resin to provide anappropriate concentration.

Next, the high-carbon-containing resin having the catalyst particlesdispersed therein may be subject to pyrolysis for curing. In particular,the resin imbedded with the catalyst particles may undergo a slowincrease in temperature, for instance, less than 1 degree C. per minute,in an inert atmosphere, such as argon, or helium. In an embodiment, thetemperature may be raised to at least between about 1000° C. and about2000° C., and more preferably about 1700° C. This slow increase intemperature, in one embodiment, allows water, the primary by-product ofthe reaction, to diffuse out of the resin material. In addition, thecatalyst material, such as ferrocene, in the presence of hightemperature, breaks down and forms, for instance, particles of ironwhich can act as a template to which carbon within thehigh-carbon-containing resin can attach. The attachment of carbon to thetemplate particles and the subsequent attachment to the existing carbonon the template particles occurs in series, so as to lead to the growthof a nanotube from a particle, and the formation of an array of carbonnanotubes within the resin. The result can be the formation of acomposite material having a glassy carbon matrix reinforced by a“grown-in” array of carbon nanotubes. As illustrated in FIG. 3, scanningelectron micrographs of the surface of a composite material manufacturedin accordance with this embodiment of the invention show the presence ofan array of multiwall carbon nanotubes 31. In an embodiment, the processcan generated substantially aligned nanotubes (see FIG. 6).

To the extent necessary, the activity of the catalyst particles (e.g.,iron particles) may need to be augmented. In one embodiment of theinvention, thiophene (C₄H₄S) or another sulfur containing compound, forexample, may be added to the resin prior to or during pyrolysis toaugment the activity of the catalyst particles. In addition, it may bedesirable to add trace amount of, for instance, Nb, Mo, Cr, or acombination thereof to the resin prior to or during pyrolysis to refinethe size of the catalyst particles, in order to control the size of thenanotubes being grown.

Moreover, if desired, the glassy carbon matrix composite may be exposedto a final ramp temperature up to about 3000° C. to anneal the compositeto remove any potential defects within the composite.

It should be noted that although carbon nanotubes are disclosed herein,the present process may be implemented in a manner which includeschemically modifying the carbon in whole or in part, or by replacing thecarbon with, for instance, silicon, boron or nitrogen, so that nanotubescan be generated containing elements other than or in addition tocarbon. For instance, the nanotubes may be silicon-carbon nanotubes,boron-carbon nanotubes, nitrogen-carbon nanotubes, or a combinationthereof.

The in situ composite having a glassy carbon matrix reinforced by a“grown-in” array of carbon nanotubes created in accordance with theabove process may have a wide variety of applications based not only onmechanical properties, but also on chemical and electrical properties.Unlike other types of fiber composites, this type of in situ composite,for instance, can be cast into complex three-dimensional shapes orstructures, coated on a substrate, provided as a thin film, or extrudedas a filamentous fiber, then subsequently paralyzed to form the desiredstructure or coating fiber. It should be noted that liquid viscositywould not be substantially changed, since the nanotubes are grown withinthe structure after polymerization, followed by pyrolyzation.

For extrusion as a filamentous fiber, in one embodiment, the catalyzedresin may be extruded through a nozzle having an aperture at atemperature ranging from about 50° C. to about 150° C. to polymerize anexiting mono-filament or fiber. In accordance with an embodiment, thenozzle or aperture may be provided with a diameter of from about 0.5microns to about 500 microns to extrude a mono-filament of similar size.Upon subsequent pyrolization at temperature ranging from about 1000° C.to about 2000° C., followed by a ramp up temperature of up to about3000° C., the extruded mono-filament can be converted into a filament ofglassy carbon with a substantial amount of carbon nanotubes along itslength.

In addition, properties of the structure, coating or extrusion formedfrom this in situ composite can be tailored by changing the catalystconcentration or material within the composite, coating thin film, orfilament. For example, silicon may be added to the outer portions of astructure, so as to form an oxidation-resistant coating of siliconcarbide upon pyrolyzation. These capabilities can lead to the creationof devices, such as heart valves or blood vessel stents, as well ascomponents (i.e., parts) of a device, including medical and surgicaldevice. These devices or components, in one embodiment, may be providedwith nanotubes in the high strength area, since nanotubes are known tohave relatively high strength, and pure glassy carbon matrix in areassubject to harsh chemical environments or in areas wherebiocompatibility can be important, since glassy carbon matrix canwithstand such environments.

For example, a RESOL resin, catalyzed as described above, may initiallybe placed in a reusable mold designed to produce an embossed pattern ofstent 40 illustrated in FIG. 4. This mold, in an embodiment, may beformed in two parts and can be made of silicon rubber. One part, theinterior mold, can contain the pattern, while the other part, theexterior mold, can hold the resin. The mold may then be placed in avacuum chamber, and evacuated to a rough vacuum. Thereafter, the resinmay be placed in the mold, in a manner well know in the art of casting.The mold and resin may next be very slowly heated to the temperature ofabout 150° C., at which the resin polymerizes, and subsequently allowedto cool to form a glassy carbon precursor. The now polymerized glassycarbon precursor may thereafter be carefully removed from the mold, andreheated at a temperature range of from about 1000° C. to about 2000° C.at a rate of less than 1 degree per minute to form the desiredstructure. It should be appreciated that a faster rate of increase intemperature may be possible since this type of structure can be thin andwater may diffuse out of the structure rapidly. Other parts or devicescan be cast in a similar manner.

In an alternate embodiment where a relatively thicker structure may benecessary, the high-carbon-containing resin may be provided as anaerosol. The high-carbon-containing resin aerosol may be sprayed, forinstance, in the presence of a catalyst, onto a hot substrate. In thepresence of heat from the substrate, formation and growth of carbonnanotubes, in the manner noted above, can be initiated. Such an approachwould allow the build up of thicker, substantially more uniformcomponents or devices, especially when the substrate may be rotating andthe component being manufactured needs to be centro-symmetric.

Applications

The composite material generated from either of the processes above maybe provided with more than about 5% carbon nanotubes by weight and maybe utilized in a variety of applications.

Referring now to FIGS. 4A-B, there is shown a stent 40 made from thecomposite materials described above. The stent 40, in an embodiment,includes a substantially tubular body 41 having a pathway 413 extendingbetween ends 411 and 412. The tubular body 41, in one embodiment, may bemade to include an expandable matrix 42 having intersecting filaments 43to permit stent 40 to transition between an elongated or collapsed state(FIG. 4A) prior to insertion into an artery or vessel (e.g., a bloodvessel) and an expanded state (FIG. 4B) subsequent to insertion into theartery or vessel. It should be appreciated that matrix 42 may bepatterned in any number of ways, so long as it permits tubular body 41to move between a collapsed state and an expanded state insertion.Examples of matrix patterns that may be employed are illustrated inFIGS. 5A and 5B.

Since stent 40 may be made from the composite materials described above,looking now at FIG. 6, each filament 43, in an embodiment, may beprovided with carbon nanotubes 60 towards the interior of filament 43,so as to provide stent 40 with sufficient strength. In addition, eachfilament 43 may be provided with glassy carbon material 61 about thenanotubes 60 towards the exterior of filament 43 to permit interactionwith fluid within the vessel. Since pathway 42 of tubular body 41 may bedefined by the exterior of filaments 43, the presence of thebiocompatible glassy carbon material thereat permits pathway 42 tointeract with the fluid within the vessel in a biocompatible manner.

Furthermore, since each of the provided nanotubes 60 may be grown from acatalyst particle, such as an iron catalyst, each nanotube 60 mayinclude a catalyst particle 63 at one end, that is, the end from whichgrowth was initiated. The presence of the catalyst particles 63 withinthe interior of filaments 43 can allow stent 40 to be visible, forinstance, in an x-ray to permit a high degree of accuracy when locatingor placing the stent 40 within the vessel. To further enhance visibilityof stent 40, additional contrast agents can easily be added within theinterior of filaments 43. Examples of contrasting agents that may beused include BaO, TaO₂, WO₃, HfO, WC, Au nano or micro-powders, or acombination thereof. In this application, the presence of iron catalystscan also serve to provide the stent 40 with magnetic properties.Magnetic properties, of course, can be imparted when catalysts withmagnetic properties are used.

Tubular body 41, in an embodiment, may further include an exteriorsurface 44 that can be patterned. By providing tubular body 41 with apatterned exterior surface 44, movement of stent 40 along or within avessel may be minimized, since the patterned surface 44 may act toanchor tubular body 41 against a surface of the vessel. It should benoted that a variety of patterns on the exterior surface 44 may beemployed in connection with tubular body 41, so long as such patternscan minimize or prevent movement of stent 40 within the vessel. FIGS.7-8 illustrate various patterned designs that may be employed inconnection with the exterior surface 44, including a ratchet pattern(FIGS. 7A-B), or other patterns, for instance, etched lines, swirls orany other geometric shapes, such as those illustrated in FIG. 8.

Expansion of the tubular body 41 of stent 40 may be accomplished by anymethods known in the art, for instance, a balloon device, or by the useof shape-memory technology that can allow the tubular body 41 toautomatically expand subsequent to insertion into the vessel. Moreover,expansion of stent 40 can further permit the patterned exterior surface44 of stent 40 to better engage interior walls of the vessel withinwhich the stent 40 may be placed to hold and maintain the stent 40 inplace. In an embodiment, the pressure exerted radially by the geometryof stent 40 may be governed by the holding power of the patternedexterior surface 44 as well as the elastic properties of the composite.

It should be noted that although reference is made to a stent, otherbiocompatible and implantable biomedical devices may be made using thecomposite materials set forth in the present invention. For instance,anchoring screws for use in ACL and PCL reconstruction and otherorthopedic implants.

The processes illustrated above, along with the composite materialgenerated therefrom, can be utilized for other applications ormanufacturing of other devices. For example, the process may be used toform ballistic armor. In one embodiment, the ballistic armor may beformed by initially coupling or layering commercially available bodyarmor textile fabric or textile made from carbon nanotubes, yarnscreated from the carbon nanotubes, or carbon nanotube webs or belts.Next, a catalyzed resin, as described above, may be used to coat orcouple a plurality of body armor textile fabric sheets and hold thesheets together, so as to contribute to the strength of the armor, aswell as help to minimize or prevent cracks in the armor. The coatedsheets may be pyrolyzed to generate the end product.

Other applications may include: (1) molded high strength parts, such ascombat helmets, motorcycle helmets, football helmets and the like, (2)aerospace parts being used for high temperature applications, such asleading edges for hypersonic use, rocket nozzles etc., (3) motor parts,such as brake pads and bearings, (4) sporting goods, such as rackets,golf clubs, bicycle frames, (5) parts for use at substantially hightemperature, including thermal conductors, electrical conductors,structural lightweight panels, and coatings for graphite, so as toreduce cost, while maintaining a high strength wear resistant surface,(6) engraving plates made from glassy carbon that can be highlyresistant to wear and corrosive properties of inks used in intaglio orother forms of printing, and (7) biocompatible implantable parts orcomponents, such as heart valves and stents, graded so that the glassycarbon matrix comes substantially into contact with body fluids, whilethe nanotube portions can be located in center regions or core areas ofthe composite and in high stress areas.

While the invention has been described in connection with the specificembodiments thereof, it will be understood that it is capable of furthermodification. Furthermore, this application is intended to cover anyvariations, uses, or adaptations of the invention, including suchdepartures from the present disclosure as come within known or customarypractice in the art to which the invention pertains.

1. A method for manufacturing a composite material, the methodcomprising: providing a sheet of non-woven nanotubes having voidsbetween the nanotubes; infiltrating the voids between the nanotubes witha resin material; placing the infiltrated sheet into an inertatmosphere; and exposing the infiltrated sheet to a temperature range offrom about 1000° C. to about 2000° C. to transform the infiltrated sheetinto the composite material.
 2. A method as set forth in claim 1,wherein, in the step of providing, the nanotubes are carbon nanotubes.3. A method as set forth in claim 1, wherein the step of infiltratingincludes coating the sheet with a fluid resin material.
 4. A method asset forth in claim 3, wherein, in the step of coating, the fluid resinmaterial is furfuryl alcohol.
 5. A method as set forth in claim 1,wherein the step of infiltrating includes melting a sheet of a polymericresin material onto the non-woven sheet.
 6. A method as set forth inclaim 5, wherein, in the step of melting, the sheet of resin materialincludes one of RESOL resin, polyamide resin, epoxy resin, Kraytonresin, polyethylene resin, polyaryletherketone resin, or a combinationthereof.
 7. A method as set forth in claim 1, wherein, in the step ofplacing, the inert atmosphere includes argon, helium, or other inertgases.
 8. A method as set forth in claim 1, wherein, in the step ofexposing, the temperature is about 1700° C.
 9. A method as set forth inclaim 1, wherein the step of exposing includes raising the temperatureat a rate of from less than 1 degree to about 1 degree C. per minute.10. A method as set forth in claim 1, wherein the step of exposingincludes diffusing a fluid by-product from the sheet.
 11. A method asset forth in claim 1, wherein the step of providing includes layering aplurality of non-woven sheets on one another.
 12. A method as set forthin claim 11, wherein the step of infiltrating includes coating eachnon-woven sheet on a heated substrate, so that curing of the resin canoccur before the next non-woven sheet can be layered thereonto.
 13. Amethod as set forth in claim 11, wherein the step of infiltratingincludes positioning a sheet of a polymeric resin between adjacentnon-woven sheets.
 14. A method as set forth in claim 13, wherein, in thestep of positioning, the sheet of polymeric resin between one pair ofadjacent non-woven sheets is different than the sheet of polymeric resinbetween another pair of adjacent non-woven sheets to provide differentproperties in different areas of the resulting composite material.
 15. Amethod as set forth in claim 11, further including bonding the pluralityof non-woven sheets to one another to provide a formed mass.
 16. Amethod as set forth in claim 11, wherein the step of bonding includesapplying heat to the layer of sheets at a temperature ranging from about125° C. to about 350° C.
 17. A method as set forth in claim 11, furtherincluding subjecting the formed mass to a final ramp temperature up toabout 3000° C. 18-24. (canceled)
 25. A method for manufacturing acomposite material, the method comprising: providing a carbon-containingresin material; adding an appropriate concentration of catalystparticles to the carbon-containing resin material; subjecting thecatalyzed resin to a temperature range of from about 1000° C. to about2000° C.; allowing carbon in the resin to couple to the catalystparticles; and permitting subsequent growth, within the resin material,of an array of carbon nanotubes from the catalyst particles, so as toresult in the formation of the composite material.
 26. A method as setforth in claim 25, wherein, in the step of providing, the resin materialincludes alkyl-phenyl formaldehyde.
 27. A method as set forth in claim25, wherein, in the step of adding, the concentration of catalystparticles ranges from about 0.005 percent to about 5 percent by weightof catalyst particles to carbon in the resin material.
 28. A method asset forth in claim 25, wherein, in the step of adding, the catalystparticles includes one of ferrocene; iron nano-particles; ironpentacarbonyl; nano-particles of magnetic transition metals or theiralloys; oxides, nitrates or chlorides of these metals; any combinationof the oxides with reducible salts; or organometallic compounds of thesemetals.
 29. A method as set forth in claim 25, wherein the step ofadding includes adding a sulfur containing compound to the catalyzedresin to augment subsequent activities of the catalyst particles whenthe catalyzed resin is subject to high temperature.
 30. A method as setforth in claim 25, wherein the step of adding includes adding one of Nb,Mo, Cr, or a combination thereof to the catalyzed resin to refine thesize of the catalyst particles, in order to control the size of thenanotubes being grown.
 31. A method as set forth in claim 25, whereinthe step of adding includes adding different catalyst particles indifferent areas of the resin material to subsequently provide differentproperties in is different areas of the resulting composite material.32. A method as set forth in claim 25, wherein the step of subjectingincludes placing the catalyzed resin into an inert atmosphere havingargon, helium, or other inert gases.
 33. A method as set forth in claim25 wherein, in the step of subjecting, the temperature is about 1700° C.34. A method as set forth in claim 25, wherein the step of subjectingincludes raising the temperature at a rate of from less than 1 degree C.to about 1 degree C. per minute.
 35. A method as set forth in claim 25,wherein the step of subjecting includes diffusing a fluid by-productfrom the resin.
 36. A method as set forth in claim 25, wherein, in thestep of permitting, the attachment of carbon to an existing carbon onthe catalyst particle occurs in series, so as to lead to the growth of acarbon nanotube from a catalyst particle.
 37. A method as set forth inclaim 25, further including subjecting the composite material to a finalramp temperature up to about 3000° C. 38-47. (canceled)
 48. A stent forplacement within a vessel, the stent comprising: a tubular expandablematrix having a plurality of intersecting filaments; a plurality ofnanotubes situated within a core of each filament; a glassy carbonmaterial situated about the nanotubes; and a pathway extending from oneend of the tubular matrix to an opposite end to permit fluid within thevessel to flow therethrough and having a surface defined by the glassycarbon material.
 49. A stent as set forth in claim 48, further includinga patterned surface about the tubular matrix to permit the matrix toengage against a surface of the vessel to minimize its movement withinthe vessel.
 50. A stent as set forth in claim 48, further including acatalyst particle at an end of each nanotube, such that the particlescan act as a contrasting agent.
 51. A stent as set forth in claim 50,wherein the catalyst particle at the end of each nanotube provides thestent with magnetic properties.
 52. A method for manufacturing acomposite fiber, the method comprising: providing a carbon-containingresin material; adding an appropriate concentration of catalystparticles to the carbon-containing resin material; extruding thecatalyzed resin material into a filamentous fiber at a temperature thatpermits polymerization of the filament; subjecting the extrudedfilamentous fiber to a temperature range of from about 1000° C. to about2000° C.; allowing carbon in the resin to couple to the catalystparticles; and permitting subsequent growth, within the resin material,of an array of carbon nanotubes from the catalyst particles, so as toresult in the formation of the composite fiber.
 53. A method as setforth in claim 52, wherein, in the step of extruding, the temperature isat a range of from about 50° C. to about 150° C.
 54. A method as setforth in claim 52, wherein, in the step of extruding, the fiber has adiameter ranging from about 0.5 microns to about 500 microns.
 55. Acomposite material comprising: a glassy carbon matrix; a plurality ofcatalyst particles dispersed throughout the matrix; and an array ofnanotubes positioned entirely within the matrix and whose presencewithin the matrix resulted from their growth from the catalyst particleswithin the matrix, so as to provide the glassy carbon matrix with addedstructural integrity.
 56. A composite material as set forth in claim 55,wherein the nanotubes include one of carbon nanotubes, silicon-carbon,boron-carbon nanotubes, nitrogen-carbon nanotubes, or a combinationthereof.
 57. A composite material as set forth in claim 55, wherein theglassy carbon matrix is capable of being formed into a three dimensionalshape or structure having the array of nanotubes therein.
 58. Acomposite material as set forth in claim 55, wherein the glassy carbonmatrix is capable of being formed as a thin film or coating having thearray of nanotubes therein.
 59. A composite material as set forth inclaim 55, wherein the glassy carbon matrix is capable of being extrudedinto a filamentous fiber having the array of nanotubes therein.
 60. Acomposite material as set forth in claim 55, wherein the glassy carbonmatrix is capable of being formed into molded high strength components.